Sang-Rok Moon
Electronics and Telecommunications Research Institute, South Korea
Title: CFO compensation method for coherent optical OFDM system by electro-optic feedback
Biography
Biography: Sang-Rok Moon
Abstract
We investigate feasibility of carrier frequency off set (CFO) compensation method using optical feedback path for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. CFO compensation is one of most important issues in OFDM system, since the CFO breakes orthogonality among OFDM subrarriers and it causes critical degradation in signal quality. In CO-OFDM, the CFO tends to be high because of laser instability. Th us wide CFO compensation range is essential. Recently proposed CFO compensation algorithms provide wide CFO estimation range. Th ey compensate CFO aft er anlog-to-digital convertor (ADC). Then, CFO compensation range is limited by sampling rate of the ADC. Th us, the sampling rate should be much higher than
CFO and/or data bandwidth. Because of high price of ADC, it is not aff ordable in practical CO-OFDM. To solve this problem, we propose a CFO compensation method having optical feedback path. Th e measured CFO is used to control local oscillator’s wavelength for CFO compensation. Since the CFO is compensated before ADC, the compensation range is not aff ected by the ADC. Residual CFO can be compensated by conventional CFO compensation methods. Th e feasibility of the proposed method is experimentally investigated. We showed that the practical CFO compensation range can be extended to the sampling frequency range, regardless of sampling rate of ADC. Although the proposed method is based on OFDM, the proposed method works in all coherent modulation formats with minor modifi cation.